Delay plunger assembly for artillery type fuses



Jan. 29, 1957 R. P. MARSHALL 2,779,286

DELAY PLUNGER ASSEMBLY FOR ARTILLERY TYPE FUSES Filed July 15, 195s HTTDENEYS United States Patent O M DELAY PLUNGER ASSEMBLY FOR ARTILLERY TYPE FUSES Robert P. Marshall, Falls Church, Va.

Application July 15, 1953, Serial No. 368,240

Claims. (Cl. 102-76) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

The present invention relates generally to fuses, and more particularly to an impact responsive delay plunger assembly.

ln the type of fuses which are provided with a delay plunger assembly having a stationary tiring .pin and a movable plunger it is usual to lock the movable plunger until the projectile is in flight so that on impact the movable plunger may be forced through inertia to contact the stationary firing pin. lf the plunger is unrestrained it may creep forward under its own weight to contact the stationary element and explode the shell in flight, or if held in the unarmed position until impact, one or all of the locking members may be driven back to a safe position to eifectually prevent'movement of the plungenand thus render the fuse inoperative.

Itis therefore a primary object of the invention to provide a delay plunger assembly increasing the sensitiveness of inertia delay functioning of the fuse.

Accordingly it is an object of the invention to provide a delay plunger assembly having a variable strength locking device allowing only a limited creep of the plunger during air travel.

A further object is to simplify structural features and reduce to a minimum number `the parts employed, to the end that the delay plunger assembly may be manufactured at low cost and the parts readily assembled and effectively retained in the prepared safety condition prior to tiring.

A practical embodiment of the invention as applied to Y an artillery point detonating fuse is illustrated in the accompanying drawings, wherein:

Figure l is a fragmentary longitudinal sectional view of a fuse showing a delay plunger assembly constructed in accordance with the invention;

Figure 2 is a cross section taken along the line 2--2 of Figure 1.

Figure 3 is a fragmentary sectional view showing one of the spring urged locking detents in locking position;

Figure 4 is a sectional view showing the position of the plunger after impact.

Referring more particularly to the drawings in which like reference numerals refer to like parts throughout the different views, 1 designates a point detonating fuse threaded at 2 for attachment to a projectile 3. The head of the fuse is provided with a super quick detonating element 4. The flash tube 5 extends from the detonating element 4 to a chamber 10 formed in the fuse body. The bore of the ilash tube is normally obstructed by a transverse spring urged setting plunger 8 which acts as a safety device and which moves outwardly under the inuence of centrifugal force during ilight. The plunger can be set for super quick ring action in which it moves outwardly or for delay action in which the plunger is locked in its obstructing position.

2,779,286 Patented Jan. 29, 1957 lCCL Mounted in the fuse body chamber 10 is the delay plunger assembly which will now be described in detail. Lining the upper portion of the cavity is a cup shaped liner 14 having an aperture 24 registering with the ash tube bore. An annular detent housing 1S which is y mounted in an offset portion of the chamber 10 surrounds ing element 12 is mounted in the plunger to one side of apart.

the ilash duct 6 and is in alignment with a firing pin 13 located on the inner surface of the liner.

' The portion of the plunger below the liner contains three outwardly opening cavities 19 spaced 120 degrees "[he detent housing` contains three similar bores 16 which are in radial alignment with the cavities. The bores 16 each contain locking detents 17 which are urged into the cavities by springs 18. A ball 20 is disposed in each of the cavities and normally held against the inner end of the cavity by the spring urged detents.

To keep the plunger 9 in proper alignment so that the detonating element 12 will be tired by the pin 13, and the bores 16 and cavities 19 will be in registry, the outer end of a guide pin 21 provided in a radial bore 22in the plunger body, projects into a longitudinal slot 23 in the cup shaped liner 14.

Functioning of the device is as follows: No action will take place until suliicient rotational speed-has been established so that centrifugal force overcomes the resistance of the springs 18 and the spring of the setting plunger 8. The setting plunger will then move outwardly to open the passageway of tube 5 communicating from the point detonating element to the booster. Detents 17 will also be urged outwardly causing the balls 20 to assume a' position where their centers will be somewhat within the periphery of the plunger element 9. The device is now in unlocked or armed position. The plunger 9 may creep forward for a limited distance, the creep being limited by the forward edges of the bores 16 contacting the surfaces of the three balls 20. In the event that rotation of the round decreases to the extent of allowing the strength of the locking detent springs 18 to overcome centrifugal force, the detents will be prevented from entering the cavities 19 as the plunger 9 has moved forward a sufficient distance to obstruct the return` of the locking detents as the bores 16 and 'cavities 19 are now out of register.

Upon impact, the super quick action element 4 will detonate the booster 7. However, should the super quick action fail, the shell will function with delay action rather than become a dud. Also, the setting plunger 8 can be locked in position so as to obstruct the flash tube 5 and only the delay plunger assembly will function to detonate the booster. As seen best in Figure 4, the plunger element 9 will be driven forward upon impact causing the balls 20 to be cammed into the cavities 19 in the plunger thus freeing the plunger 9 to move in its forward position bringing the detonator element 12 against the ring pin 13 thus tiring the shell. Detonating element 12 is always held in alignment with the tiring pin 13 due to the slot 23 and pin 21.

Thus it is seen that a plunger element has been devised, more positive in action, economical in manufacture and easily adapted to replacement of existing parts.

While a specific embodiment of the invention has been shown and described, it will be understood that various a delay plunger llongitudinally slidable in said vchamber,-

a detonator carried bysaid plunger, aiiringlpin'lixed in said body and in normallyspaced relation-with said detonator, and detent means to maintain said plunger against appreciable forwardcreep during projectile flight, said means comprising a plurality yof circumferentially spaced radial cavities formed in saidplungen a plurality of circumferentially spaced Aradial b oresformed in said body in radially axial -registrywith said cavities,aballjmovable infeach'passage'formed bytfhe-registry ofrespective-bores and cavities, and Aa -springpressed detent in-'each bore normally urging'said'ballinto its respective cavity,;said spring pressed-detent yielding-to:centrifugalforceto permit radial ballmotion-to -a position-inpart within said respective borewhereby-saideplunger will creep 'to la limited degree until motion isarrested-by engagementbetween said ball andssaidl'bore.

2; In a detonating fuse the combination jcomprising a body member, a chamber lformed -in-saidl'bodymember, a delay plunger coaxially disposedand jlongitudinally slidable in -said chamber, a `detonator carried'by said plunger, a vfiring pinliXed Iin "said: body and "in normally spaced relationwith said detonatorfand detent'rneansto maintain said plunger k'againstappreciable longitudinal creep duringprojectile Hight, said V'detent means comprising a plurality offcircumferentiallyspaced radial b ores formedV insaid body and openingintosaid chambery a plurality of circumferential'ly `spaced *radial vcavities formed in said plunger'an'd opening-into the'onter surface thereof inaxiallyaligned communication with'said bores, a ball disposed in each passage4 formed byrespective bores and cavities anda yspringpressed pin inl said bore normally=urging -said yhall radially inward into said cavity land yielding 'to centrifugal 'force whereby said ball advances -radially vduring projectile flight in'part at least'withinrsaid bore and 'limited -plungenmotion is `allowed.

3. Ina percussion fuze for arspin type projectile the combination comprising a body member havinga iirst radial bore, a chamber formed in said bodya"iiring pin in said chamberya delay action plunger slidableiri` said chamber'andfhaving a second radial bore coaxial with said `rst`bore, thererbeing a detonator in said plunger in axial alignment with Vsaid tiring fpin, centrifugally operated spring pressed detent `means in said first bore for locking-said plunger in normal safejposition, v-andfball meansv in .saidfsecond bore -andfprojected partly into said rst bore under the linfluence of centrifugal-force, holding'said plunger vforflimited -creep during cHight ofthe projectile and releasing ;said-plunger onimpact for forward :movement to ignite said -detonator, fwhen forward inertia of the projectile ceases,

`combination `comprising -a body member, a Ychamber formed in said body member, a rearwardly extending firing pin in the forward end of said chamber, a delay action plunger axially slidable in said chamber, there being a detonator in saidplunger in axial alignment with said firing pin, said plunger having a rst radial bore in itsperiphery, .a ixeldannular detent housing surrounding said plunger and having a ,second yradial bore therein in axial registry with the Iirst bore, a spring pressed detent in the second boreand pressed intoftheiirst bore to lock said plunger ytopsaid.annulardetent housing in normal safe position, and a ball in the first radial bore inwardly of said detent, limiting radially inwardl'movement of said springpressed vdetent in normal position, said detent limiting outward radial movement of said ball under the influence of spin, to a position in which its greater portion remains within the rst radial bore during flight of the projectile.

5. -Ina-peicussionfuze for a `spin type projectile the combination comprising Ya bogdy member, a chamber formed in said body member, a rearwardly extending tiring 1pin in the forward end of-sai'dk chamber, a delayA actionfplungeraxially slidable in said chamber, there1being a detonator in said plunger in axial alignment wit-h said firing pin, :said plunger #having .fa irst radiaLbore inits outer-periphery, -a xed annular detent housing'surrounding.sai'd plunger` and.y having a=second radial bore-therein infaxial :registry .with the rst bore, a spring presseddetent inthesecond radialbore andextending into the first radialibore to lock saidplunger to said annular detent housing innormalsafe position, v.and a ball in the first radial -boreinw'ardly of said detent limiting radially inwardfmovementfof ,saidI spring pressed detent, said detent limitingtoutward.radialmovement of said ball under the inuence, of spinto `a position in which its `greater yportion remains within the iirst radialrbore during flight of the projectilethe outer surface of the. lesser portion of said ballengaging the forward wall of'saidsecondradial bore to effect limited forward creep-of Isaid plunger lin flight andto release said -plungeron impact with a target when saidballiscammed inwardlyby the said forward wall when, residual vforward energy in `said plunger i overcomes centrifugal energy in said balls.

Alrlefex'encesCited inthele of this patent UNlTED STATES APATENTS Germany Sept. 4, '.1922 

